The invention pertains to the field of providing a stop apparatus and method for gear actuators, including for example gear actuators that are used to rotate a valve between open and closed positions. Such stops may be used to define a particular stop point beyond which the valve member cannot be moved.
Gear actuators are in wide use in many applications such as commercial industrial applications. In particular, gear actuators having an input shaft are used to drive a rotary valve member within a valve body.
In some applications, the drive assembly will have a reduction gear so that several turns of the input shaft will rotate the output shaft at a slower speed. The drive assembly also sometimes contains some form of rotary indicator, which may rotate with the output shaft, on the outside of the housing of the drive assembly. The indicator indicates a relative rotary position of the output shaft. Since the output shaft is attached to the rotary valve member, the indicator can show the relative position of the valve member in the valve body.
In many circumstances, such as for example, in the case of plug valves, butterfly valves and ball valves, the valve member is rotatable through a angular range from fully opened to fully closed positions. Often, this range is approximately 90 degrees of rotation.
Sometimes it is desirable to provide some form of stop arrangement that will stop the movement of the valve member in one or the other directions of travel. For example, it may be desirable to provide a stop that prevents the valve from being opened past a predetermined partially open position.
A variety of stop mechanisms that are attached to the actuator are known. Some of these are adjustable to some degree. For example, it has been known to provide a cam type member mounted to the output shaft that rotates with the output shaft and stops the output shaft when it abuts against a pin extending from the housing. The relative angular position of the cam member can be adjusted, sometimes in incremental steps.
Another approach to adjustment has been to incorporate parts having matched teeth so that the teeth can be matched at angular intervals. However, these devices may require a screw or other device to compress the two parts together.
The approaches described above are relatively complex and also suffer the disadvantage that the stop is directly connected to the output shaft.
A further disadvantage of these arrangement is that the stop must withstand the maximum output actuator torque rating. The output torque in a reducing gear actuator will be greater than the input torque, and hence it would be desirable to have a stop that can conveniently be used on the input shaft side of the gear actuator. Further, it would be desirable to have a stop that requires a minimum number of parts, and one that can be easily retrofitted to existing gear actuators.
It is therefore a feature and advantage of the present invention to provide a convenient and effective stop assembly and method for gear actuators. The above and other features and advantages are achieved through the use of a novel stop assembly and method as herein disclosed.
In accordance with one embodiment of the present invention, a stop apparatus is provided for use with a gear actuator has an input shaft and an output shaft. The stop apparatus has a stop screw mounted to rotate with the input shaft. The stop apparatus also has a stop nut mounted to threadably travel on the stop screw, and a stop guide attached to the stop screw that prevents rotation of the stop screw relative to the gear actuator and permits longitudinal travel of the stop screw during rotation of the input shaft.
In accordance with another embodiment of the present invention, a stop apparatus is provided for use with a gear actuator having an input shaft and an output shaft. The stop apparatus has a first engaging means mounted to rotate with the input shaft. The stop apparatus also has a second engaging and traveling means mounted for engaging the first engaging means and traveling on the stop screw. Guiding means is attached to the first engaging means for guiding the second engaging means. The guiding means prevents rotation of the second engaging means relative to the gear actuator and permits longitudinal travel of the stop screw during rotation of the input shaft.
In accordance with yet another embodiment of the present invention, a method for stopping a gear actuator output shaft is provided. The method includes steps of rotating an input shaft to cause a nut to travel thereon; preventing rotation of the nut relative to the input shaft; and contacting the nut with a stop surface at a predetermined degree of rotation of the input shaft.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.